Researchers at the University of Gothenburg have made an extraordinary leap by creating micrometer-scale gears powered by laser light.
Microscopic Gears Powered by Light: Revolutionizing Mini Machines
Micromotors are tiny mechanical devices that perform rotation at a microscopic scale. Researchers recently created an innovative micromotor powered by optical metasurfaces, which are special layers engineered to control light with high precision. This micromotor uses silicon, a common material in technology, and functions when illuminated with uniform linearly polarized light, meaning the light waves vibrate in a single plane.
The main structure, called a metarotor, is shaped like a ring containing the metasurface and is anchored firmly to a glass chip by a small capped pillar. When light hits the metasurface, it changes direction, creating forces that spin the metarotor in one direction. This conversion of light into mechanical motion offers exciting possibilities for controlling devices on tiny scales.
How Light Creates Movement
By deflecting incoming light, the metasurface generates a force acting in the opposite direction because of momentum conservation laws. The ring’s design includes four segments with different orientations of nanoscale blocks called meta-atoms. These segments create forces that combine to produce torque — the twisting force needed to rotate the micromotor counterclockwise.
The Fabrication Process
The micromotors are manufactured through advanced techniques such as electron beam lithography and specialized etching. The process involves several steps: forming the silicon metasurface with nano-sized meta-atoms; etching a supporting silicon dioxide ring; creating and capping a pillar to suspend and anchor the rotor; and finally, removing sacrificial layers, allowing free rotation. Remarkably, this method can produce tens of thousands of these micromotors on a chip just 5 mm square.
The Advantages and Potential Impact
This new approach overcomes past challenges where powering microscopic gears relied heavily on electric or magnetic fields, requiring bulky connectors or specific materials. The use of uniform illuminated light not only allows miniaturization but also helps avoid interference issues common with other methods.
Moreover, these micromotors can reach angular velocities that depend on both their design—such as the number of meta-atoms—and the intensity of incident light. At higher intensities, water heating around them lowers viscosity, which leads to even faster rotation speeds thanks to reduced drag forces.
Why Does This Matter?
The development opens doors for multiple cutting-edge applications such as microrobotics, microfluidic devices, force sensors, and reconfigurable optical systems. With scalable production possible using standard semiconductor manufacturing techniques, integrating complex, microscopic geared machines into future technologies becomes more feasible than ever before.
The Power of Optical Metamaterials
The team created gears with special patterns called optical metamaterials. These materials control light on a very small scale. By shining a laser on these microscopic gears made from silicon, they caused the gears to spin. The speed and direction of the microscopic gear’s movement can be controlled simply by changing how intense the light is or how it is polarized (the light’s wave orientation). This method skips the bulky mechanical connections that were holding back progress.
A Continuous Journey Toward Smaller Machines
This research represents an important step toward controlling mechanical movements at micro- and nanoscale levels using purely optical means. It sets up exciting future opportunities for engineering smaller machines capable of performing tasks previously unimaginable due to size limitations.
Reference
- Wang, G., Rey, M., Ciarlo, A., Shanei, M., Xiong, K., Pesce, G., Käll, M., & Volpe, G. (2025). Microscopic geared metamachines. Nature Communications, 16(1). https://doi.org/10.1038/s41467-025-62869-6
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Neha Adikane holds a Master’s degree in Environmental Science from Pune University, bringing a unique blend of scientific expertise and creative writing skills to her craft. She specializes in creating engaging, insightful, and impactful content across various niches. With a passion for translating complex ideas into simple, relatable narratives, she excels at crafting blogs, articles, website content, and social media posts that captivate readers and drive engagement. Neha’s background in environmental science adds depth to her writing, allowing her to effectively cover topics related to sustainability, eco-awareness, and scientific innovations.